Abstract: Five physiological indexes(leaf proline content, K+/Na+, Cl- content, SOD activity, and MDA content) were chosen to evaluate the comprehensive salt tolerance of Populus euphratica and Tamarix spp. in natural riparian forest by subordinate function in Yuli County. With the increase of soil salinity, the leaf proline content of P. euphratica increased, its K+/Na+ did not change, the Cl- content and SOD activity increased then decreased, MDA content decreased. However, the leaf proline content, K+/Na+, SOD activity and MDA content of Tamarix spp. increased and its Cl- content decreased. The leaf proline content of P. euphratica was significantly higher than Tamarix spp. in three plots (pP. euphratica and Tamarix spp. were 902.70 and 732.99 μg·g-1. The leaf K+/Na+ and MDA content of Tamarix spp. were significantly higher than that of P. euphratica in plots 1 and 2 with higher soil salt content in 0-10 cm depth (p+/Na+ of P. euphratica and Tamarix spp. were 0.060 and 0.095 and the leaf MDA content of P. euphratica and Tamarix spp. were 8.23 and 13.96 μmol·g-1. The leaf Cl- content of P. euphratica was significantly higher than that of Tamarix spp. in plot 1 and 2 (p- content of P. euphratica and Tamarix spp. were 2.59 and 1.49 μg·mg-1 in plot 2. The leaf SOD activity of Tamarix spp. (0.43 U·mg-1·min-1) was significantly higher than that of P. euphratica (0.37 U·mg-1·min-1) in plots 1 (pP. euphratica is higher than that of Tamarix spp., according to the results of subordinate function. The salt tolerance mechanism is different in two plants: P. euphratica tolerates salt by increasing leaf proline and decreasing leaf Cl- content, whereas Tamarix spp. tolerates salt by increasing leaf proline content, improving leaf K+/Na+ and enhancing SOD activity under higher soil salinity condition.